GNAS

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GNAS

A locus on chromosome 20q13.3 that has a highly complex imprinted expression pattern, giving rise to maternally, paternally and biallelically expressed transcripts derived from four alternative promoters and 5' exons. Some transcripts have a differentially methylated region (DMR) at their 5' exons. This DMR is commonly found in imprinted genes and correlates with transcript expression; one transcript produced from this locus and the antisense transcript are paternally expressed, noncoding RNAs, which may regulate regional imprinting. Alternative splicing of downstream exons results in different forms of the stimulatory G-protein alpha subunit, a key component of the classical signal-transduction pathway linking receptor-ligand interactions to adenylyl cyclase activation and various cellular responses.

Molecular pathology
GNAS mutations have been linked to pseudohypoparathyroidism types 1a and 1b, Albright hereditary osteodystrophy, pseudopseudohypoparathyroidism, McCune-Albright syndrome, progressive osseus heteroplasia, polyostotic fibrous dysplasia of bone and pituitary tumours.
References in periodicals archive ?
Fibrous dysplasia is a developmental tumor like sporadic condition that results from a post zygotic mutation in GNAS1 (Guanine Nucleotidebinding Protein, a stimulating activity polypeptide 1) gene.
Isolated PTH resistance (PHPIb) can result from mutations within the GNAS1 gene but is more commonly caused by epigenetic imprinting abnormalities affecting the upstream exon 1A (9).
Fibrous dysplasia is a sporadic condition that results from a postzygotic mutation in the GNAS1 (guanine nucleotide binding protein, a - stimulating activity polypeptide1) gene.
The abnormal production of fibroconnective tissue is due to a mutation in the GNAS1 gene.
It is associated with a somatic mutation in the GNAS1 gene, encoding a stimulatory Gs-[alpha] protein.
In its molecular etiology, activating mutations in the GNAS1 gene localized on the long arm of the 20th chromosome are involved and this activiation which is reflected to G-protein alpha subunit leads to endocrine pathologies.
The down regulation of the GNAS1 gene via siRNA leads to the increased expression of Cbfa1 that would stimulate the production of bone-differentiating proteins such as osteopontin, collagen I, and osteocalcin [3, 15].
1 The exact etiology of fibrous dysplasia is uncertain although it may be caused due to non-inherited condition by mutation in GNAS1 gene (guanine nucleotide binding protein) or abnormalities in AMPc which may result in increased proliferation of melanocytes causing cafeu-lait spots and hyperfunction of effected endocrine organs.
GNAS1 mutations occur more commonly than previously thought in intramuscular myxoma.
6,7 Type II PHP is characterized by increased PTH, hypocalcemia, hyperphosphatemia and absolute lack of physical somatic features of AHO, further unique differentiating features is a normal cAMP response to PTH infusion but a deficient phosphaturic response indicating a defect distal to c AMP generation in renal cells and normal GNAS1 activity.
Este sindrome es causado por mutaciones en el gen GNAS1 y esta asociado con el mosaicismo, es decir, que el gen anormal esta presente en una fraccion y no en todas las celulas del paciente.
Similar to PanIN of the pancreas, BilIN corresponds to flat IN of the bile duct, and it shares molecular alterations of KRAS and TP53 in multistep carcinogenesis; however, it does not harbor GNAS1 mutations, in contrast to IPNB.